"The decision came down to whether KG wanted to keep playing," a source told the Herald. "And once he decided that he did, it was going to be Boston. He wasn’t going to leave Doc (Rivers) and those guys and play anywhere else."

Garnett's return to the NBA was uncertain after 17 seasons in the league. The 36-year-old has played in 1,255 games, logging almost 47,000 minutes. The reported three-year deal will expire when Garnett is 39-years-old.

Some thought Garnett might retire after this past season, but he returned to top form in this year's playoffs, averaging 19.2 points and 10.3 rebounds as the Celtics advanced to Game 7 of the Eastern Conference Finals before losing to the Miami Heat.

The Celtics roster is now beginning to take shape, with Garnett, Paul Pierce, Rajon Rondo, Avery Bradley, JaJuan Johnson, and rookies Jared Sullinger, Fab Melo, and Kris Joseph in the fold. NBA free agency opens Sunday at midnight, and it is expected that the Celtics will try to bring back Jeff Green among others.